In recent years, wearable smart devices especially flexible wearable devices attract more and more researches and uses. The flexible wearable device such as flexible cellphone can be worn on a user's waist, and also can be taken off from the waist, which is convenient to carry. When the flexible cellphone is worn on a waist, the user usually lifts his waist so as to raise the flexible cellphone worn on the waist to make a call, puts the flexible cellphone beside an ear to answer a call, and moves the flexible cellphone beside the mouth to speak. In the whole process of the call, the user needs to frequently move his waist back and forth, which is troublesome.